THE AURORA. 7 



"We already begin to see, then, that auroras are 

 associated in some mysterious way with the action of 

 the solar rays. The phenomenon which had been looked 

 on for so many ages as a mere spectacle, caused perhaps 

 by some process in the upper regions of the air, of a 

 simply local character, has been brought into the range 

 of planetary phenomena. As surely as the brilliant 

 planets which deck the nocturnal skies are illuminated 

 by the same orb which gives us our days and seasons, 

 so they are subject to the same mysterious influence 

 which causes the northern banners to wave resplen- 

 dently over the star-lit depths of heaven. Nay, it is 

 even probable that every flicker and coruscation of 

 our auroral displays corresponds with similar manifes- 

 tations upon every planet which travels round the sun. 

 It becomes, then, a question of exceeding interest to 

 inquire what is the nature of the mysterious appari- 

 tion which from time to time illuminates our skies. 

 We have learnt something of the laws according to 

 which the aurora appears ; but what is its true nature ? 

 What sort of light is that which illuminates the 

 heavens ? Is there some process of combustion going 

 on in the upper regions of our atmosphere ? Or are 

 the auroral streamers electric or phosphorescent ? Or, 

 lastly, is the light simply solar light reflected from 

 some substance which exists at an enormous elevation 

 above the earth ? 



All these views have from time to time found sup- 

 porters among scientific men. It need hardly be said 

 that what we now know of the association between 



